1. Field of the Invention
The present invention relates to a micro-actuator operated by electrostatic force and a manufacturing method thereof, and more particularly, to a micro-actuator driven in a see-saw motion in an axial direction and a manufacturing method thereof.
2. Description of the Related Art
U.S. Pat. No. 5,025,346 discloses a micro-actuator operated by the electrostatic force induced by the structure of a comb-type electrode. The micro-actuator disclosed in U.S. Pat. No. 5,025,346 has a structure with a plurality of moving comb-type electrodes and a plurality of fixed comb-type electrodes arranged alternately on a moving structure and a fixed structure, respectively. The moving structure is suspended by a surrounding supporting structure and the suspended structure is driven at a resonant frequency in the horizontal direction.
To drive in the direction of more than 1 axis such as the x-axis and the y-axis, if driving is in one direction along one axis, more than 3 electrodes are needed in the driving part, and if driving is in both directions along one axis, at least 5 electrodes are needed. U.S. Pat. No. 5,536,988 discloses an actuator that is fabricated using a modified single crystal reactive etching and metalization process which incorporates an isolation process utilizing thermal oxidation of the device.
In the prior micro-actuator, the driving comb-type electrodes are arranged in a direction parallel to the plane of the stage of a moving body or a moving structure, and the fixed comb-type electrodes are arranged on a fixed structure, alternating with the driving comb-type electrodes and parallel to the plane of the stage in the same way as the driving comb-type electrodes.
Since the comb-type electrodes are arranged in the neighborhood of the stage in the prior micro-actuator as described above, the total size is expansive compared to the stage or the moving structure. The prior micro-actuator has a structure driven in the direction of an axis or two axes (x, y-axis) parallel to the plane of the stage or the moving structure, and the application is thus limited.
Korean patent application no. 98-37315 and Korean patent application no. 99-20488 that claims the priority based on the latter application disclose a micro-actuator with a see-saw driving method in one axial direction. The applications disclose a micro-actuator applicable to an optical disk drive. This micro-actuator may be applied to various fields as an optical scanner as well. However, this see-saw driving micro-actuator has a stage back driving structure where the driving comb-type electrodes and the fixed driving comb-type electrodes are arranged at the back of the stage and on the top of the plate corresponding to the back, and since the top and bottom structures are manufactured using two substrates and these are joined together afterward, the manufacture is not easy. Particularly, it is difficult to join the top and bottom structures if foreign materials exist on at least one of the driving comb-type electrodes and the fixed comb-type electrodes arranged in each structure. Therefore, there is a need to provide a structure where the top and bottom structures can be processed separately and joined successfully, and a method for its manufacture.